The goal of this project is to understand how neurons establish their proper dendritic fields. For this purpose, we study the phenomenon of dendritic tiling in the peripheral nervous system (PNS) of Drosophila melanogaster. In tiled systems, such as the mammalian retina and Drosophila PNS, the dendritic fields of functionally similar neurons show strict avoidance, and thus partition a large receptive area (the retina or body wall, respectively) into several mini-domains. The multidendritic neurons in the Drosophila PNS comprise several independent tiled systems. We are testing the hypothesis that each of these systems provides and responds to distinct repulsive signals that allow like dendrites to recognize and avoid each other without recognizing non-like dendrites. We have developed a series of cell-type specific markers that uniquely label the distinct subsets of tiling neurons with Green Fluorescent Protein (GFP). These markers will be used to: 1) visualize neurons for ablation studies in live embryos and examine changes to the dendritic field areas of neighboring neurons, 2) examine candidate genes for their role in tiling and, 3) conduct a mutagenesis screen to identify and characterize novel genes involved in tiling and dendritic morphogenesis. These studies will identify how dendritic arbors decide when to stop growing and when to continue or resume their growth, processes that are essential for the proper wiring of nervous systems during development and regeneration.